System for filling and emptying of heat exchangers

ABSTRACT

With outdoor erected surface heat exchangers care has to be taken of filling up and emptying in cold weather since the cooler liquid may freeze in in the heat exchanger tubes and destroy them. Thus, quick filling up and emptying is necessary. This is obtained by employing a communication line with a regulating flap between a supply conduit connected to the inlets of the heat exchangers, and a reflux conduit connected to the outlet thereof. The communication conduit has an oblique position inclined towards the supply conduit so that the regulating flap in it will be closed only in normal operation of the system where the flap of the device is pressed down on its seat by the overpressure prevailing in the supply conduit with respect to the reflux conduit. The advantage of the arrangement consists in that the heat exchangers can be filled up in the reverse direction and emptied through a drain conduit quickly and with simultaneous deareating and air introduction, respectively. Moreover, a relatively lesser number of component parts is required.

United States Patent 1191 Heller et al.

111 3,825,060 1451 July 23,1974

[ SYSTEM FOR FILLING AND EMPTYING OF HEAT EXCHANGERS [75] Inventors:Laszlo Heller; Laszlo Forgo; Mihaly Horvath, all of Budapest, Hungary[73] Assignee: TRANSELEKTRO Magyar Villamossagi Kulkerskedelmi Vallalat,Budapest, Hungary [22] Filed: Nov. 2, 1972 [21] Appl. No.: 303,166

[30] Foreign Application Priority Data Nov. 5, 1971 Hungary EE 1969 [52]US. Cl 165/11, 137/520, 137/521, 137/527.8, 165/71 [51] Int. Cl F16tl/34 [58] Field of Search..... 165/11, 71; 137/519, 527.8,, 9 137/597[56] References Cited UNITED STATES PATENTS 1,039,749 10/1912 Ingram1147/519 2,891,773 6/1959 Heller 165/71 3,519,068 7/1970 Harris et al.261/29 Primary Examiner--Manuel A; Antonakas Assistant Examiner-DanielJ. OConnor Attorney, Agent, or Firm-Blum Moscovitz Friedman & Kaplan157] q ABSTRACT With .outdoor erected surface heat exchangers care hasto be taken of filling up and emptying in cold weather since the coolerliquid may freeze in in the heat exchanger tubes and destroy them. Thus,quick filling up and emptying is necessary.

, This is obtained by employing a communication ,line

with a regulating flap between a supply conduit connected to the inletsof the heat exchangers, and a reflux conduit connected to the outletthereof. The communication conduit has an oblique position inclinedtowards the supply conduit so that the regulating flap in it will beclosed only in normal operation of the system where the flap of thedevice is pressed down on its seat by the overpressure prevailing in thesupply conduit with respect to the v reflux conduit.

The advantage oi the arrangement consists in that the heat exchangerscan be filled up in the reverse direction and emptied through a drainconduit quickly and simultaneous deareating and air introduction,

Trespectively'. Moreover, a relatively lesser number oflcomponent-partsis required.

l 5 Claims, 4 Drawing Figures PATENTEDJULZBISM sum 1 or 2 3 0 EXCHANGERSThis invention relates to a system for filling and emptying' of heatexchangers, particularly of the doublefiow type.

As is known, the employment of air cooled surface heat exchangers forrecooling the cooling water eg, of steam turbine power plants is rapidlygaining ground. Their operation or starting is a relativelysimple matterin fair weather. However, if the weather is cold the starting of heatexchangers expecially of the multi-flow type may strike upon seriousdifficultiesand'may even cause damagesI NameIy, the heat exchangerscomprise a great number of parallelly connected tubes. The bank of tubesin which the waterflows downwards in operation may freeze in if the'heatexchanger is not properly dea erated and the airtrapped in the tubeshappens to I interrupt the flow of water.

- In order to obtain a suitable deaerationthe heat exchangers ought tobe filled up with water slowly. With slow filling up, however, the waterintroduced into the cold heat exchangersmay freeze in in the tubes or ina part thereof duringsuch filling. Therefore, in cold weather, fillingup has to be carried out quickly and with ensuring a perfect deaeration.

It has been suggested to obtain; such deaeration by filling up the heatexchangers in the reverse direction. It means that e.g., double-flowheat exchangers provided with inlet and outlet valves and erected in theopen air are filled up in such a manner that first the outlet valve ofthe heat exchanger is opened so that, thereby, first the return branchthereof is filled up in a direction which is opposite to the directionof normal operational water flow. The inlet valve of the heat exchangeris opened only subsequentlyand with a certain delayQBy suchmethod, allbanks of tubes (flows) of the heat exchanger the filling up liquid willflow in upward direction and will push out the air in front of it. Suchdisplaced air may withdraw through air escape valves provided on top theheat exchangers and no air will be trapped in the return flows orbranches thereof which might cause 'opertional troubles and deterioratethe heat transmission capacity or cause the cooling water to freeze inindividual tubes and destroy the heat exchanger in cold weather.Obviously, if air bubbles are trapped in the forward branch or flow ofthe heat exchanger, they will be carried towards the air escape valvesonce normal-water flow sets in. On the other hand, an air bubble in thereturn branch or flow would try to approach the air escape valve byflowing in a direction whichis opposite to the direction of normal flowand would be prevented from such upward displacement by the downwardlydirected normal flow of the cooling medium. The result is that the airbubble stays 'at theplace where it has been trapped and forms an airplugwhich stops the water flow in the respective tube. By filling up inthe re verse direction referred to above such stopping by air bubblesmay be obviated.

Current practice of filling up in the reverse direction consists inproviding individual double flow heat ex changers or groups of suchparallelly connected heat exchangers with four shut-off means such asvalves operated manually or automatically. Of these means, a

pair is destined to serve forshutting-off the cooler liqcreasing thedelay in opening the entrance side shut-off while another pair servesfor draining the cooler liquid from bothflows thereof. In case ofautomatic program control, an opening of the shut-off means at theentrance is, e.g., by employing a time switch, delayed with respect tothe opening of the shut-off means at the exit.

It has been found that such filling up inthe reverse direction ishandicapped by that the pressure prevailing on the exit side of the heatexchanger is smaller than individual heat exchangers or heat exchangergroups I are being filled up oneafter the other. Thus, the delay inopening the entrance shut-off means can in before be adjusted to anaverage value only which ensures a complete deareation at filling up allheat exchangers and heat exchanger groups without, however, permittingto obtain theshortest possible period of filling time.

* Though, filling up in' the reverse direction and inmeans increases thereliability of deaeration, such delay entails temperature strains in theheat exchangers since one of their flows is filled up by warm coolingwater employed for filling up purposes while the other flow will bewarmed up later due to the delay referred to above. 1

The main object of the present invention is to obviate the aforesaiddifficulties without abandoning the principle of reverse. filling upwhich may be carried out quickly and without temperature strains causedby operational delays.

..The system for filling up and emptying heat exchangers of themultiflow type comprises, in combination, a heatexchanger with aninlet-and an outlet for a cooling liquid, associated each with anotherflow of the heat exchanger, a supply conduit connected to said inlet, areturn conduit connected to said outlet, and a drain conduit branchingoff said supply conduit; shut-off means being provided in'each of saidsupply conduit, return to the accompanying drawings which show, by wayof 7 example, various embodiments of the system according to theinvention and in which:

' FIG. 1 is a connectiondiagram showing one embodiment of the systemaccording to the invention.

FIG. 2 is a longitudinal sectioanl view of a regulating flap.

FIGS. 3 and 4 are connection diagrams of further exemplified embodimentsof the system according to the invention. t

Same reference characters refer to similar details throughout thedrawings.

In the drawing, FIG, 1 shown a system comprising a series of heatexchangers 8 connected in parallel between a supply conduit ordistributing line 6 and a return conduit or collecting line 7. A drainconduit 17 branches off the supply conduit 6. All three conduits 6, 7and 17 are'provided with shut off means such as valves 1, 2 and3,'respectively. Reference numeral refers to automatic air escape valveson top the heat ex changers 8. Y Y

In compliance with the invention, a communication conduit 9 isprovidedbetween the supply conduit 6 and the return conduit 7 whichcomprises a regulating flap 4 arranged for permitting a flow from thereturn conduit 7 into the supply conduit 6 whereas a flow in theopposite direction is prevented thereby. With the representedembodiment, this is obtained by that the regulating flap '4 is disposedin an oblique portion of the communication conduit inclined toward thesupply conduit 6 as shown in FlGJl.

Such inclined position of the communication conduit duit 6 will causethe valve disk to settle down on its seat 11 and to interrupt the flowpath along the communication conduit 9.

In operation, a cooler liquid such as cooling water is admitted throughthe open shut off valve 1 into the supply conduit 6. After havingtraversed the heat exchangers 8 the cooling water withdraws through thereturn conduit 7 and the open shut off valve 2 is indicated by arrows.The regulating flap 4 in the communication conduit 9 is closed so thatno cooling water will flow from the return conduit 7 into the supplyconduit 6 through the communication conduit 9 which would mean ashort-circuiting of the system.

If the system has to be emptied, shutoff valves 1 and 2 are closed andthe shut off valve 3 is opened. Then, the cooler liquid will be drainedfrom the heat exchangers 8 through both the supply conduit 6 and thereturn conduit 7 as well as the communication conduit 9 and the drainconduit 17. Ambient air is automatically permitted to enter the heatexchangers 8 through the air escape valves 5 so as to prevent thegeneration of vacuum in the system and, thereby, to prevent the waterfrom flowing out of the heat exchangers 8.

On the other hand, when the system is to be filled up,

the shut off valve 3 in the drain conduit 17 is closed while the shutoff valve 2 in the return conduit 7 is opened with the shut off valve 1in the supply conduit 6 left closed. Then, warm cooling water will enterthe exit sides or flows (banks of tubes) of the heat exchangers 8through the return conduit 7 pushing the air in front of them out of theheat exchangers 8 through the air escape valves 5 into the ambiency.

Meanwhile, the warm cooling water flows through the communicationconduit 9 and its open valve 4 also into the supply conduit 6 above theclosed shut off valve 1 and-begins to fill up the entrance side or flow(bank of tubes) of the heat exchanger 8 as well. Such filling up isdelayed by the resistance of the regulating flap 4 and the communicationconduit 9 which will 9 permits to employ simple regulating flaps such asthe other hand, a pressure increase in the supply conhave been selectedaccordingly. The rising water dispels the air also from theentrancesides or flows of the heat exchangers 8 through the air escape valves 5.

When the heat exchangers 8 are completely filled up with warm coolingliquid, the shut off valve 1 will be opened at an optional speed wherebycirculation of the cooling liquid is set in. At the same time, theregulating flap 4 is closed by the pressure difference which appearsbetween the pressure prevailing in the supply conduit 6 and the pressureprevailing in the return conduit 7, the former being higherv than thelatter due to the pressuredrop along the conduits and the heatexchangers. v I

FIG. 3 shows an embodiment of the system according to the inventionwhich differs from the previous one in several respects.

It will be seen that, instead of one regulating flap 4, there is a pairof such flaps in parallel connection. Ob-

viously, more than two parallelly connected regulating flaps 4 might beemployed as well. The employment of more than one regulating flaps 4with their associated communication conduits 9 results in an increasedreliability of operation.

Furthermore, in'the instantcase the system is provided with a timepattern control means such as program control unit 12 which isoperatively connected to the shut off valves 1, 2 and 3 by means'ofactuators 13, '14 and 15, respectively, as suggested by dotted lines inthe drawing. Thepr ogram control unit 12 ensures an automatic operationof the system in such amanner that after the shut off valve 3 beingclosed, first the actuator 13 of shut off valve 2 is given an openingimpulse whereafter with a certain delay obtained e.g., by means of atime relay the actuator 14 of shut off valve 1 is operated so .thatthe'above described sequence of valve operation is obtainedautomatically.

FIG. 4 illustrates an exemplified embodiment which is dinstinguishedfrom the previous one, apart from employing a single regulating flap 4,by the program control unit .12 being connected to a feeler 16 forascertaining the level of coolingwater in the heat exchangers 8. Whenthe heat exchangers 8 are all filled up with water, opening impulse isgiven by the program contorl unit 12to the shut off valve 1 in'thesupplyconduit 6 whereupon normal operation of the system is entailed asdescribed above.

Hereinbefore,the invention has been described in connection with threeheat exchangers 8. Obviously, more or less heat exchangers or groups ofsuch heat exchangers might be provided with a filling up and emptyingsystem according to the invention.

Moreover, the represented embodiments have been provided with automaticair escape valves. Instead of such valves, stand pipes connected toindividual conduits or to a common conduit might be arranged on top theheat exchangers.

It will be seen that the system according to the invention isdistinguished by a seriesof advantages.

The various flows and more particularly the banks of tubes of the heatexchangers connected to the supply conduit and to the return conduit,respectively, will be v is suitably delayed by the regulating flap 4with respect exchangers associated with and connected to the sup-' plyconduit 6 be filled up with cooling water which, then, spilling overinto the downward flows would reach the return conduit and would preventa proper deaerationof that part of the system.

The time period of opening of the shut off valve 1 may be selectedoptionally and has not to beadapted to filling conditions.

Filled up condition of the heat exchangers may be ascertained byrelatively simple means suchas swimmers which operate switches.Moreover, in case of automatic control, impulses given by such swimmeroperated switches may be used for triggering the opening procedure ofshut off valve 1.

If a plurality of heat exchangers or groups thereof are employed inparallel connection, the system according to the invention permits areliable deaeration even if individual heat exchangers or groups thereofare started in sequence- I In addition, the amount of the cooler liquidtraversing already started heat exchangers will not be altered by theamount of cooler liquid used for and by the speed of filling up.

In order to ensure complete emptying of the system the communicationconduit 9 comprising the regulating flap 4 is connected to the deepestpoint of the return conduit 7 and is disposed at an inclined positionwith respect to the supply conduit 6 so that the valve disk 10 normallydoes not engage its seat 11 as has been explained above. Therefore, theregulating flap 4 does not require any pressure difference for beingopened and for the cooler liquid being entirely drained off the returnconduit 7. The inclination of the regulating flap 4 is selected so thatthe pressure difference appearing in normal operation of the system andcaused mainly by the flow resistance in the heat exchangers will keepthe regulating flap 4 in its closed position.

Finally, the system according to the invention has the advantage thatonly three shut off means rather than four have to be operated manuallyor distance controlled.

What we claim is: 1. A system for filling and emptying of multiflow heatexchangers comprising, in combination, a heat exchanger with an inletand an outlet for a cooling liquid,

associated each with another flow of the heat exchanger,a supply conduitconnected to said inlet, a return conduit connected to said outlet, adrain conduit branching'off said supply conduit, shut off means in eachof said supply conduit, return conduit and drain conduit, acommunication conduit connecting said supply conduit with said returnconduit, and a regulating flap in said communication conduit arrangedfor permitting a flow from said return conduit into said supply conduit,and to prevent a flow in the opposite direction.

2. In a system for filling and emptying of multiflow heat exchangers asclaimed in claim 1 the further improvement of said regulating flap beingdisposed in an oblique portion of said communication conduit inclinedtoward said supply conduit so as to be opened in inoperational positionof the systemand closed in operation thereof where the pressureprevailing in said supply conduit is higher than the pressure in saidreturn conduit due to the pressure drop in the heat exchangersu 3. In asystem for filling and emptying of multiflow heat exchangers as claimedin claim l, the further improvement of the provision of means foropeningthe shut off means in said return conduit prior to opening theshut off means in said supply conduit so as to fill up the heatexchangers through said return conduit.

4. In a system for filling an emptying of multiflow heat exchangers asclaimed in claim 3 the further improvement of the provision of a timepattern control means comprising a feeler for triggering the opening ofthe shut off means in said supply conduit, said feeler being arrangedfor yielding a triggering impulse upon said heat exchangers being filledup with cooler liquid.

provided in parallel connection.

1. A system for filling and emptying of multiflow heat exchangerscomprising, in combination, a heat exchanger with an inlet and an outletfor a cooling liquid, associated each with another flow of the heatexchanger, a supply conduit connected to said inlet, a return conduitconnected to said outlet, a drain conduit branching off said supplyconduit, shut off means in each of said supply conduit, return conduitand drain conduit, a communication conduit connecting said supplyconduit with said return conduit, and a regulating flap in saidcommunication conduit arranged for permitting a flow from said returnconduit into said supply conduit, and to prevent a flow in the oppositedirection.
 2. In a system for filling and emptying of multiflow heatexchangers as claimed in claim 1 the further improvement of saidregulating flap being disposed in an oblique portion of saidcommunication conduit inclined toward said supply conduit so as to beopened in inoperational position of the system and closed in operationthereof where the pressure prevailing in said supply conduit is higherthan the pressure in said return conduit due to the pressure drop in theheat exchangers.
 3. In a system for filling and emptying of multiflowheat exchangers as claimed in claim 1, the further improvement of theprovision of means for opening the shut off means in said return conduitprior to opening the shut off means in said supply conduit so as to fillup the heat exchangers through said return conduit.
 4. In a system forfilling an emptying of multiflow heat exchangers as claimed in claim 3the further improvement of the provision of a time pattern control meanscomprising a feeler for triggering the opening of the shut off means insaid supply conduit, said feeler being arranged for yielding atriggering impulse upon said heat exchangers being filled up with coolerliquid.
 5. In a system for filling and emptying of multiflow heatexchangers as claimed in claim 2 the further improvement of a number ofsaid regulating flaps being provided in parallel connection.